Semiconductor device and method of fabricating the same

ABSTRACT

A semiconductor device includes first and second active patterns protruding upward from a substrate, a gate electrode crossing the first and second active patterns and extending in a first direction, a first source/drain region on the first active pattern and on at least one side of the gate electrode, and a second source/drain region on the second active pattern and on at least one side of the gate electrode. The first and second source/drain regions have a conductivity type different from each other, and the second source/drain region has a bottom surface in contact with a top surface of the second active pattern and at a lower level than that of a bottom surface of the first source/drain region in contact with a top surface of the first active pattern. The first active pattern has a first width smaller than a second width of the second active pattern.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. non-provisional patent application is a continuation of U.S.patent application Ser. No. 16/111,854, filed Aug. 24, 2018, which is acontinuation of U.S. patent application Ser. No. 15/288,080, filed onOct. 7, 2016, now U.S. Pat. No. 10,090,413, issued on Oct. 2, 2018,which claims the benefit of Korean Patent Application No.10-2015-0148961, filed on Oct. 26, 2015, in the Korean IntellectualProperty Office, the entire contents of each of the above-referencedapplications are hereby incorporated by reference.

BACKGROUND 1. Field

Example embodiments of the present disclosure relate to a semiconductordevice with a field effect transistor and a method of fabricating thesame.

2. Description of the Related Art

Due to their relatively small-size, multi-functionality, and/orrelatively low-cost characteristics, semiconductor devices areconsidered important elements in the electronic industry. Thesemiconductor devices may be classified into a memory device for storingdata, a logic device for processing data, and a hybrid device includingboth memory and logic elements. To meet the increased demand forelectronic devices with relatively fast speed and/or relatively lowpower consumption, semiconductor devices with relatively highreliability, relatively high performance, and/or multiple functions areneeded. To satisfy these technical requirements, semiconductor devicesrequire increased complexity and/or integration density.

SUMMARY

Some example embodiments of the inventive concepts provide asemiconductor device, in which a field effect transistor with improvedelectric characteristics is provided.

Some example embodiments of the inventive concepts provide a method offabricating a semiconductor device, in which a field effect transistorwith improved electric characteristics is provided.

According to some example embodiments of the inventive concepts, asemiconductor device includes first and second active patternsprotruding upward from a substrate, a gate electrode crossing the firstand second active patterns and extending in a first direction, a firstsource/drain region on the first active pattern and on at least one sideof the gate electrode, and a second source/drain region on the secondactive pattern and on at least one side of the gate electrode. Thesecond source/drain region may have a conductivity type different fromthat of the first source/drain region, and the second source/drainregion may have a second bottom surface in contact with a second topsurface of the second active pattern and at a lower level than a firstbottom surface of the first source/drain region in contact with a firsttop surface of the first active pattern. The first top surface of thefirst active pattern may have a first width, and the second top surfaceof the second active pattern may have a second width greater than thefirst width.

In some example embodiments, the first active pattern and the firstsource/drain region may constitute an NMOSFET, and the second activepattern and the second source/drain region may constitute a PMOSFET.

In some example embodiments, the first and second active patterns mayinclude first and second channel regions, respectively, when viewed in aplan view. The gate electrode may overlap the first and second channelregions. A surface area directly contacting the second channel regionand the second source/drain region may be greater than a surface areadirectly contacting the first channel region and the first source/drainregion.

In some example embodiments, the first and second channel regions mayhave top surfaces at a same level.

In some example embodiments, the first source/drain region may include amaterial having a first lattice constant equal to or smaller than thatof the substrate, and the second source/drain region may include amaterial having a second lattice constant greater than that of thesubstrate.

In some example embodiments, a maximum width of the first source/drainregion in the first direction may be a third width, and a maximum widthof the second source/drain region in the first direction may be a fourthwidth different from the third width.

In some example embodiments, the device may further include a deviceisolation pattern on the substrate filling a gap region between thefirst and second active patterns. The device isolation pattern mayinclude a first portion having a top surface, the gate electrode mayoverlap the first portion in a plan view, and a second portion on atleast one side of the gate electrode, and the second portion may definea recess region having a bottom surface lower than the top surface ofthe first portion.

In some example embodiments, the bottom surface of the recess region maybe lower than the first and second bottom surfaces of the first andsecond source/drain regions.

In some example embodiments, the device may further include an etch stoplayer covering the first and second source/drain regions and the deviceisolation pattern. The etch stop layer may directly cover an innersurface of the recess region.

In some example embodiments, the device may further include gate spacerson opposite sides of the gate electrode and a gate insulating patternbetween the gate electrode and the first and second active patterns, andbetween the gate electrode and the gate spacers.

According to some example embodiments of the inventive concepts, asemiconductor device includes a pair of first active patterns and a pairof second active patterns protruding upward from a substrate, deviceisolation patterns filling trenches between the first and second activepatterns, a gate electrode crossing the first and second active patternsand extending in a first direction, a pair of first source/drain regionson respective ones of the first active patterns and on at least one sideof the gate electrode, and a pair of second source/drain regions onrespective ones of the second active patterns and on at least one sideof the gate electrode. Each of the first source/drain regions has afirst bottom surface in contact with respective first top surfaces ofthe first active patterns. Each of the second source/drain regionshaving a second bottom surface in contact with respective second topsurfaces of the second active patterns. Each of the first top surfacesof the first active patterns has a first width in the first directionand each of the second top surfaces of the second active patterns has asecond width greater than the first width in the first direction.

In some example embodiments, the first active patterns may include upperportions configured to serve as channel regions of an NMOSFET, and thesecond active patterns may include upper portions configured to serve aschannel regions of a PMOSFET.

In some example embodiments, a distance between the pair of first activepatterns in the first direction may be a first length, a distancebetween the pair of second active patterns in the first direction may bea second length longer than the first length, and a distance between anadjacent pair of the first and second active patterns may be a thirdlength longer than the second length.

In some example embodiments, a surface area directly contacting acorresponding pair of the second source/drain regions and the secondactive patterns may be greater than a surface area directly contacting acorresponding pair of the first source/drain regions and the firstactive patterns.

In some example embodiments, each of the device isolation patterns mayinclude first portions overlapped by the gate electrode in a plan viewand a second portion on at least one side of the gate electrode. A firstof the second portions of the device isolation patterns may include afirst recess region between the pair of first active patterns, and asecond of the second portions of the device isolation patterns mayinclude a second recess region between the pair of second activepatterns. A bottom surface of the first recess region may be higher thana bottom surface of the second recess region.

In some example embodiments, a third of the second portions may includea third recess region between an adjacent pair of the first activepattern and the second active pattern, and the bottom surface of thesecond recess region may be higher than a bottom surface of the thirdrecess region.

In some example embodiments, the first source/drain regions may beconnected to form an integral structure defining at least one first airgap, and the first air gap may be directly enclosed by the firstsource/drain regions and the device isolation patterns.

In some example embodiments, the device may further include an etch stoplayer covering the first and second source/drain regions and the deviceisolation patterns. The etch stop layer may seal a gap region betweenthe pair of second source/drain regions to define at least one secondair gap below the second source/drain regions. The second air gap may beenclosed by the etch stop layer.

In some example embodiments, a volume of the second air gap may belarger than a volume of the first air gap.

In some example embodiments, the device may further include firstresidue patterns adjacent to interfaces between the second activepatterns and the second source/drain regions. The first residue patternsmay be between the pair of second active patterns.

In some example embodiments, at least one of the second source/drainregions may bend toward an adjacent one of the first source/drainregions.

In some example embodiments, the device may further include secondresidue patterns adjacent to interfaces between the first activepatterns and the first source/drain regions. The second residue patternsmay be on opposite sides of a lower portion of at least one of the firstsource/drain regions.

According to some example embodiments of the inventive concepts, asemiconductor device includes a substrate including a first region and asecond region spaced apart from each other, a plurality of fin-shapedfirst active patterns on the first region of the substrate and spacedapart from each other by a first distance, a plurality of fin-shapedsecond active patterns on the second region of the substrate and spacedapart from each other by a second distance smaller than the firstdistance, a first gate electrode crossing the first active patterns andextending in a first direction, a second gate electrode crossing thesecond active patterns and extending in the first direction, firstsource/drain regions on respective ones of the first active patterns andon at least one side of the first gate electrode, and secondsource/drain regions on respective ones of the second active patternsand on at least one side of the second gate electrode. The first andsecond active patterns may have the same conductivity type, the firstsource/drain regions may be spaced apart from each other in the firstdirection, and the second source/drain regions may be connected to eachother to form an integral structure arranged in the first direction.

In some example embodiments, the first and second active patterns mayinclude upper portions configured to serve as channel regions of aPMOSFET.

In some example embodiments, the first region may be an SRAM region onwhich memory cells are provided, and the second region may be a logicregion on which a logic circuit are provided.

In some example embodiments, the device may further include deviceisolation patterns filling trenches between the first active patternsand between the second active patterns, and at least one air gapenclosed by the device isolation patterns and the second source/drainregions forming the integral structure.

In some example embodiments, each of the device isolation patterns mayinclude a first portion overlapped by one of the first and second gateelectrodes, and a second portion on at least one side of the one of thefirst and second gate electrodes. A first of the second portions of thedevice isolation patterns may include a first recess region between anadjacent pair of the first active patterns, a second of the secondportions of the device isolation patterns may include a second recessregion between an adjacent pair of the second active patterns, and abottom surface of the first recess region may be higher than a bottomsurface of the second recess region.

In some example embodiments, the device may further include an etch stoplayer on the first and second regions to cover the first and secondsource/drain regions and the device isolation patterns. The air gap maybe separated from the etch stop layer.

According to some example embodiments of the inventive concepts, amethod of fabricating a semiconductor device includes patterning anupper portion of a substrate to form first and second active patternsprotruding upward from the substrate, forming a sacrificial gate patternto cross the first and second active patterns and extend in a firstdirection, recessing upper portions of the first and second activepatterns on at least one side of the sacrificial gate pattern such thatthe second active pattern has a top surface lower than a top surface ofthe first active pattern, forming first and second source/drain regionson the recessed upper portions of the first and second active patterns,respectively, the first and second source/drain regions being doped tohave conductivity types different from each other, and replacing thesacrificial gate pattern with a gate electrode.

In some example embodiments, the patterning of the upper portion of thesubstrate may include patterning an NMOSFET region of the substrate toform the first active pattern and patterning a PMOSFET region of thesubstrate to form the second active pattern.

In some example embodiments, the method may further include forming adevice isolation pattern on the substrate to fill a gap region betweenthe first and second active patterns and recessing an upper portion ofthe device isolation pattern on a side of the sacrificial gate patternto form a recess region.

In some example embodiments, the method may further include forming anetch stop layer on the substrate to cover the first and secondsource/drain regions and the device isolation pattern. The etch stoplayer may directly cover an inner surface of the recess region.

In some example embodiments, the method may further include forming agate spacer layer on the substrate and anisotropically etching the gatespacer layer to form gate spacers on opposite side surfaces of thesacrificial gate pattern.

In some example embodiments, recessing the upper portions of the firstand second active patterns may allow a portion of the gate spacer layerconfigured to serve as a residue pattern to remain on at least one ofthe recessed upper portions of the first and second active patterns.

In some example embodiments, the method may further include forming aninterlayered insulating layer on the substrate, forming contact holes topenetrate the interlayered insulating layer and expose the first andsecond source/drain regions, respectively, and forming source/draincontacts to fill the contact holes. Upper portions of the first andsecond source/drain regions may be etched when the contact holes areformed.

According to some example embodiments of the inventive concepts, asemiconductor device includes a first MOSFET structure including atleast one first active pattern protruding upward from a substrate and atleast one first source/drain region having a first bottom surfacecontacting a first top surface of the first active pattern, and a secondMOSFET structure including at least one second active pattern protrudingupward from a substrate and at least one second source/drain regionhaving a second bottom surface contacting a second top surface of thesecond active pattern and at a lower level than the first bottomsurface, the second source/drain region having a different shape thanthe first source/drain region. The first top surface of the first activepattern has a first width, and the second top surface of the secondactive pattern has a second width greater than the first width.

The first source/drain region may include a material having a firstlattice constant equal to or smaller than that of the substrate, and thesecond source/drain region may include a material having a secondlattice constant greater than that of the substrate.

A maximum width of the first source/drain region may be a third widthand a maximum width of the second source/drain region may be a fourthwidth different from the third width.

The at least one first active pattern may be a pair of first activepatterns and a distance between the pair of first active patterns is afirst length, the at least one second active pattern is a pair of secondactive patterns and a distance between the pair of second activepatterns is a second length longer than the first length, and a distancebetween the pair of first active patterns and the pair of second activepatterns is a third length longer than the second length.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingbrief description taken in conjunction with the accompanying drawings.The accompanying drawings represent non-limiting, example embodiments asdescribed herein.

FIG. 1 is a plan view illustrating a semiconductor device according tosome example embodiments of the inventive concepts.

FIGS. 2A to 2D are sectional views taken along lines A-A′, B-B′, C-C′,D-D′, and E-E′ of FIG. 1.

FIG. 3 is a plan view illustrating a method of fabricating asemiconductor device according to some example embodiments of theinventive concepts.

FIGS. 4A to 4C are sectional views taken along lines A-A′, B-B′, C-C′,and D-D′ of FIG. 3.

FIG. 5 is a plan view illustrating a method of fabricating asemiconductor device according to some example embodiments of theinventive concepts.

FIGS. 6A to 6D are sectional views taken along lines A-A′, B-B′, C-C′,D-D′, and E-E′ of FIG. 5.

FIGS. 7A to 7D are sectional views taken along lines A-A′, B-B′, C-C′,D-D′, and E-E′ of FIG. 5.

FIG. 8 is a plan view illustrating a method of fabricating asemiconductor device according to some example embodiments of theinventive concepts.

FIGS. 9A to 9D are sectional views taken along lines A-A′, B-B′, C-C′,D-D′, and E-E′ of FIG. 8.

FIG. 10 is a sectional view that is taken along line D-D′ of FIG. 1 toillustrate a semiconductor device according to some example embodimentsof the inventive concepts.

FIG. 11 is a sectional view that is taken along line D-D′ of FIG. 1 toillustrate a semiconductor device according to some example embodimentsof the inventive concepts.

FIG. 12 is a sectional view that is taken along line D-D′ of FIG. 1 toillustrate a semiconductor device according to some example embodimentsof the inventive concepts.

It should be noted that these figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiment, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION

The inventive concepts will now be described more fully hereinafter withreference to the accompanying drawings, in which example embodiments ofthe inventive concepts are shown. The inventive concepts and methods ofachieving them will be apparent from the following example embodimentsthat will be described in more detail with reference to the accompanyingdrawings. Example embodiments of the inventive concepts may, however, beembodied in different forms and should not be constructed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete, and will fullyconvey the scope of the inventive concepts to those skilled in the art.

As used herein, the singular terms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be understood that when an element is referred to asbeing “connected” or “coupled” to another element, it may be directlyconnected or coupled to the other element or intervening elements may bepresent.

Similarly, it will be understood that when an element such as a layer,region or substrate is referred to as being “on” another element, it canbe directly on the other element or intervening elements may be present.In contrast, the term “directly” means that there are no interveningelements. Additionally, the embodiment in the detailed description willbe described with sectional views as ideal example views of theinventive concepts. Accordingly, shapes of the example views may bemodified according to manufacturing techniques and/or allowable errors.Therefore, the embodiments of the inventive concepts are not limited tothe specific shape illustrated in the example views, but may includeother shapes that may be created according to manufacturing processes.

Example embodiments of the present inventive concepts explained andillustrated herein include their complementary counterparts. The samereference numerals or the same reference designators denote the sameelements throughout the specification.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements or layers should be interpreted in a likefashion (e.g., “between” versus “directly between,” “adjacent” versus“directly adjacent,” “on” versus “directly on”). As used herein the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “includes” and/or “including,” if usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, an etched region or an implanted regionillustrated as a rectangle may have rounded or curved features. Thus,the regions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the actual shape of a region of adevice and are not intended to limit the scope of example embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the inventive concepts belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 1 is a plan view illustrating a semiconductor device according tosome example embodiments of the inventive concepts. FIGS. 2A to 2D aresectional views taken along lines A-A′, B-B′, C-C′, D-D′, and E-E′ ofFIG. 1.

Referring to FIGS. 1 and 2A to 2D, a substrate 100 with a first regionR1 and a second region R2 may be provided. The substrate 100 may be asemiconductor substrate. In example embodiments, the substrate 100 maybe a silicon substrate, a germanium substrate, or a silicon-on-insulator(SOI) substrate. The first region R1 may be a part of a memory cellregion, on which a plurality of memory cells for storing data areprovided. As an example, a plurality of 6T SRAM cells, each of whichincludes six transistors, may be provided on the first region R1. Thesecond region R2 may be a part of a logic cell region, on which logictransistors constituting a logic circuit are provided. As an example,logic transistors for a processor core or I/O terminals may be providedon the second region R2. But, the inventive concepts are not limitedthereto. Hereinafter, the first region R1 will be described in moredetail.

Referring back to FIGS. 1 and 2A to 2C, the first region R1 may includea first NMOSFET region NR1 and a first PMOSFET region PR1. The firstNMOSFET region NR1 may be an active region for an n-type transistor, andthe first PMOSFET region PR1 may be an active region for a p-typetransistor. In example embodiments, the substrate 100 may include aplurality of the first NMOSFET regions NR1 and a plurality of the firstPMOSFET regions PR1 which are arranged in a first direction D1.

Active patterns AP1 and AP2 may be provided on the first region R1. Forexample, first active patterns AP1 protruding from the substrate 100 maybe provided on the first NMOSFET region NR1 of the first region R1. Thefirst active patterns AP1 may be arranged in the first direction D1 andmay be line-shaped structures extending in a second direction D2crossing the first direction D1.

Second active patterns AP2 protruding from the substrate 100 may beprovided on the first PMOSFET region PR1 of the first region R1. Thesecond active patterns AP2 may be arranged in the first direction D1 andmay be line-shaped structures extending in the second direction D2.Widths of the first and second active patterns AP1 and AP2 may increasewith increasing distance from the substrate 100, when measured in thefirst direction D1.

The active patterns AP1 and AP2 on the first region R1 may be spacedapart from each other in the first direction D1, and distances betweenthe active patterns AP1 and AP2 may be different from each other. Forexample, a pitch between the first active patterns AP1 on the firstNMOSFET region NR1 may be a first length L1, when measured in the firstdirection D1. A pitch between the second active patterns AP2 on thefirst PMOSFET region PR1 may be a second length L2, when measured in thefirst direction D1. A pitch between an adjacent pair of the first andsecond active patterns AP1 and AP2 may be a third length L3, whenmeasured in the first direction D1. The second length L2 may be longerthan the first length L1, and the third length L3 may be longer than thesecond length L2. Each of the first to third lengths L1, L2, and L3 maybe a center-to-center distance between an adjacent pair of the activepatterns.

Second device isolation patterns ST2 may be provided to fill trenchesbetween the first active patterns AP1 and between the second activepatterns AP2. In other words, the second device isolation patterns ST2may be provided to define the first and second active patterns AP1 andAP2. The first and second active patterns AP1 and AP2 may include firstand second active fins AF1 and AF2, whose top surfaces are higher thanthe second device isolation patterns ST2.

First device isolation patterns ST1 may be provided at opposite sides ofthe first NMOSFET region NR1 and the first PMOSFET region PR1. The firstdevice isolation patterns ST1 may be provided to separate the firstNMOSFET regions NR1 and the first PMOSFET region PR1 shown in FIG. 2from other MOSFET regions.

The first and second device isolation patterns ST1 and ST2 may besubstantially connected to each other to form a single insulatingpattern. A thickness of the first device isolation patterns ST1 may begreater than that of the second device isolation patterns ST2. Inexample embodiments, the first and second device isolation patterns ST1and ST2 may be formed by different processes. In example embodiments,the first and second device isolation patterns ST1 and ST2 may be formedat the same time using the same process and may have substantially thesame thickness. The first and second device isolation patterns ST1 andST2 may be formed in an upper portion of the substrate 100. The firstand second device isolation patterns ST1 and ST2 may be formed of orinclude a silicon oxide layer.

Each of the second device isolation patterns ST2 may include a firstportion P1, which is provided below a gate electrode GE to be describedbelow and second portions P2, which are provided at opposite sides ofthe gate electrode GE. Each of the second portions P2 of the seconddevice isolation patterns ST2 may have a recessed top surface. Forexample, the second portions P2 may be provided to define recess regionsRS1, RS2, and RS3. Referring back to FIG. 2C, the recess regions RS1,RS2, and RS3 may include first recess regions RS1 between the firstactive patterns AP1, second recess regions RS2 between the second activepatterns AP2, and third recess regions RS3 between the first and secondactive patterns AP1 and AP2 adjacent to each other.

The first to third recess regions RS1-RS3 may be provided to have arecess depth that is dependent on a pattern density. For example, therecess depth may be smaller between the first active patterns AP1 spacedat a small distance than between the active patterns spaced at a largerdistance. As an example, bottom surfaces of the first recess regions RS1may be higher than those of the second recess regions RS2. This may bebecause that the second length L2 is longer than the first length L1. Inaddition, the bottom surfaces of the second recess regions RS2 may behigher than those of the third recess regions RS3. This may be becausethat the third length L3 is longer than the second length L2.

Gate electrodes GE may be provided on the first and second activepatterns AP1 and AP2 to extend in the first direction D1 and to crossthe first and second active patterns AP1 and AP2. The gate electrodes GEmay cover top and side surfaces of the first and second active patternsAP1 and AP2. The gate electrodes GE may be spaced apart from each otherin the second direction D2. The gate electrodes GE may extend in thefirst direction D1 to cross both of the first and second deviceisolation patterns ST1 and ST2.

Interface layers IL may be respectively interposed between the first andsecond active patterns AP1 and AP2 and the gate electrodes GE. A gateinsulating pattern GI may be provided between a corresponding pair ofthe interface layers IL and the gate electrodes GE. Gate spacers GS maybe provided at opposite sides of each of the gate electrodes GE. Acapping pattern GP may be provided to cover a top surface of each of thegate electrodes GE. The interface layer IL may directly cover topsurfaces of the active patterns AP1 and AP2 (e.g., top surfaces ofchannel regions CH1 and CH2 to be described below). The gate insulatingpattern GI may be disposed between the gate electrode GE and the gatespacers GS. The gate insulating pattern GI may be horizontally extendedfrom the active patterns AP1 and AP2 along the gate electrode GE todirectly cover top surfaces of the first portions P1 of the seconddevice isolation patterns ST2.

In example embodiments, although not shown, the gate spacers GS may havean ‘L’-shaped section, when viewed in a sectional view taken in thesecond direction D2. For example, each of the gate spacers GS mayinclude a vertical portion covering a side surface of the gate electrodeGE and a horizontal portion covering the top surface of the activepattern AP1 or AP2.

The gate electrodes GE may include at least one of doped semiconductormaterials, conductive metal nitrides (e.g., titanium nitride or tantalumnitride), or metals (e.g., aluminum or tungsten). The interface layer ILmay include a silicon oxide layer. The gate insulating patterns GI mayinclude at least one of a silicon oxide layer, a silicon oxynitridelayer, and high-k dielectric layers (e.g., hafnium oxide, hafniumsilicate, zirconium oxide, or zirconium silicate) having dielectricconstants higher than that of the silicon oxide layer. Each of thecapping patterns GP and the gate spacers GS may include at least one ofa silicon oxide layer, a silicon nitride layer, or a silicon oxynitridelayer.

Source/drain regions SD1 and SD2 may be provided on the first and secondactive patterns AP1 and AP2 positioned at opposite sides of each of thegate electrodes GE. For example, first source/drain regions SD1 may beprovided on the first active patterns AP1 at opposite sides of each ofthe gate electrodes GE. Second source/drain regions SD2 may be providedon the second active patterns AP2 at opposite sides of each of the gateelectrodes GE. As an example, the first source/drain regions SD1 on thefirst NMOSFET region NR1 may have n-type conductivity, and the secondsource/drain regions SD2 on the first PMOSFET region PM may have p-typeconductivity.

The first active fins AF1 on the first active patterns AP1 may havefirst channel regions CH1 interposed between the first source/drainregions SD1. The second active fins AF2 on the second active patternsAP2 may have second channel regions CH2 interposed between the secondsource/drain regions SD2. Each of the first channel regions CH1 mayconnect a pair of the first source/drain regions SD1 with each other.Each of the second channel regions CH2 may connect a pair of the secondsource/drain regions SD2 with each other. The first and second channelregions CH1 and CH2 may be positioned below and overlapped with the gateelectrodes GE.

The first and second source/drain regions SD1 and SD2 may be epitaxialpatterns, which are respectively grown using the first and second activepatterns AP1 and AP2 as a seed layer. In example embodiments, the firstsource/drain regions SD1 may include a material capable of exerting atensile strain to the first channel regions CH1, and the secondsource/drain regions SD2 may include a material capable of exerting acompressive strain to the second channel regions CH2. For example, inthe case where the substrate 100 is a silicon substrate, the firstsource/drain regions SD1 may include a SiC layer having a latticeconstant smaller than Si or a Si layer having substantially the samelattice constant as the substrate 100. The second source/drain regionSD2 may include a SiGe layer having a lattice constant larger than Si.

In a sectional view, the first source/drain regions SD1 may have adifferent shape from the second source/drain regions SD2, as shown inFIG. 2C. As described above, this is because the first and secondsource/drain regions SD1 and SD2 are formed of different materials grownthrough an epitaxial growth process. For example, the maximum width inthe first direction D1 of the first source/drain regions SD1 may be athird width W3, and the maximum width in the first direction D1 of thesecond source/drain regions SD2 may be a fourth width W4 that isdifferent from the third width W3.

In example embodiments, the first source/drain regions SD1 may beprovided to have the maximum widths W3 different from each other. Forexample, in the case where the first source/drain regions SD1 are formedof Si, the first source/drain regions SD1 may grow in an irregularmanner. As a result, the first source/drain region SD1 may have a shapeor size which varies depending on its position. In addition, although,in FIG. 2C, the fourth width W4 is illustrated to be greater than thethird width W3, but the inventive concepts are not limited thereto. Forexample, the third width W3 may be greater than the fourth width W4.

The bottom surfaces of the first source/drain regions SD1 may bepositioned at a first level BL1, and the bottom surfaces of the secondsource/drain regions SD2 may be positioned at a second level BL2. Here,the first level BL1 may be higher than the second level BL2. Inaddition, both of the first and second levels BL1 and BL2 may be higherthan the bottom surfaces of the recess regions RS1-RS3.

The first active patterns AP1 may include first top surfaces TSa1, whichare in direct contact with the bottom surfaces of the first source/drainregions SD1, and second top surfaces TSa2, which serve as top surfacesof the first channel regions CH1. The second active patterns AP2 mayinclude first top surfaces TSb1, which are in direct contact with thebottom surfaces of the second source/drain regions SD2, and second topsurfaces TSb2, which serve as top surfaces of the second channel regionsCH2. The first top surfaces TSa1 and TSb1 of the first and second activepatterns AP1 and AP2 may not be flat and may have a downward curved orrounded profile. Here, the first top surfaces TSa1 and TSb1 may be lowerthan the second top surfaces TSa2 and TSb2.

The first top surface TSa1 of the first active pattern AP1 may have afirst width W1 and the first top surface TSb1 of the second activepattern AP2 may have a second width W2, when measured in the firstdirection D1. Here, the second width W2 may be greater than the firstwidth W1. This is because the first and second active patterns AP1 andAP2 have downward increasing widths and the first top surface TSb1 ofthe second active pattern AP2 is positioned below the first top surfaceTSa1 of the first active pattern AP1.

Because the second source/drain regions SD2 are grown using the firsttop surfaces TSb1 of the second active patterns AP2 as a seed layer, thesecond source/drain regions SD2 may have a volume that is relativelylarger than that of the first source/drain regions SD1. Thisconfiguration may allow for an increase in a magnitude of thecompressive strain to be exerted to the second channel regions CH2 fromthe second source/drain regions SD2 and an increase in a contact areabetween the second source/drain regions SD2 and the second channelregions CH2. Accordingly, increasing carrier mobility of the secondchannel regions CH2 and reducing resistance of the second channelregions CH2 may be possible.

An etch stop layer 125 may be provided on the substrate 100. The etchstop layer 125 may cover top surfaces of the first and second deviceisolation patterns ST1 and ST2. For example, the etch stop layer 125 maycover inner surfaces of the recess regions RS1-RS3 of the second deviceisolation patterns ST2. In addition, the etch stop layer 125 may coverthe first and second source/drain regions SD1 and SD2 and may extend tocover opposite side surfaces of the gate spacers GS. The etch stop layer125 may include a material having an etch selectivity with respect to afirst interlayered insulating layer 130. As an example, the etch stoplayer 125 may include a silicon nitride layer or a silicon oxynitridelayer.

The first interlayered insulating layer 130 may be provided on thesubstrate 100 to fill gap regions between the gate electrodes GE. Thefirst interlayered insulating layer 130 may have a top surface thatsubstantially coplanar with those of the capping patterns GP. In someexample embodiments, the first interlayered insulating layer 130 mayfill the recess regions RS1-RS3 provided with the etch stop layer 125. Asecond interlayered insulating layer 150 may be provided on the firstinterlayered insulating layer 130. The first and second interlayeredinsulating layers 130 and 150 may be formed of or include a siliconoxide layer.

Source/drain contacts CA may be provided at opposite sides of each ofthe gate electrodes GE. The source/drain contacts CA may be provided topass through the second interlayered insulating layer 150, the firstinterlayered insulating layer 130, and the etch stop layer 125 and maybe electrically connected to the first and second source/drain regionsSD1 and SD2. When viewed in a plan view, each of the source/draincontacts CA may be provided to cross at least one of the first activepatterns AP1 or at least one of the second active patterns AP2.

Each of the source/drain contacts CA may include a first conductivepattern 160 and a second conductive pattern 165 on the first conductivepattern 160. The first conductive pattern 160 may be a barrierconductive layer. As an example, the first conductive pattern 160 mayinclude at least one of a titanium nitride layer, a tungsten nitridelayer, or a tantalum nitride layer. The second conductive pattern 165may be a metal layer. As an example, the second conductive pattern 165may include at least one of tungsten, titanium, or tantalum. Althoughnot shown, a metal silicide layer may be interposed between each pair ofthe source/drain contacts CA and the first and second source/drainregions SD1 and SD2. The metal silicide layer may include at least oneof titanium silicide, tantalum silicide, or tungsten silicide.

Hereinafter, the second region R2 will be described in more detail. Forconcise description, an element described with reference to the firstregion R1 may be identified by a similar or identical reference numberwithout repeating an overlapping description thereof. A vertical sectionof the second region R2 taken in the second direction D2 may be similarto that of the first region R1 described with reference to FIG. 2A.

Referring back to FIGS. 1 and 2D, the second region R2 may include asecond NMOSFET region NR2 and a second PMOSFET region PR2. In someexample embodiments, n-type transistors may be integrated on the secondNMOSFET region NR2, and p-type transistors may be integrated on thesecond PMOSFET region PR2. The second region R2 may include a pluralityof the second NMOSFET regions NR2 and a plurality of the second PMOSFETregions PR2 which are arranged in the first direction D1. The secondNMOSFET region NR2 may be separated from the second PMOSFET region PR2by the first device isolation patterns ST1.

Active patterns AP1 and AP2 may be provided on the second region R2. Forexample, the first active patterns AP1 protruding from the substrate 100may be provided on the second NMOSFET region NR2 of the second regionR2, and the second active patterns AP2 protruding from the substrate 100may be provided on the second PMOSFET region PR2 of the second regionR2.

The first and second active patterns AP1 and AP2 on the second region R2may be spaced apart from each other by substantially the same space. Asan example, when measured in the first direction D1, a pitch between thesecond active patterns AP2 on the second PMOSFET region PR2 may be afourth length L4 and a pitch between the first active patterns AP1 onthe second NMOSFET region NR2 may be a fifth length L5. Here, the fourthlength L4 may be substantially equal to the fifth length L5. The fourthlength L4 may be smaller than the second length L2 described above.

The second device isolation patterns ST2 may be provided to filltrenches between the first active patterns AP1 and trenches between thesecond active patterns AP2 on the second region R2. Each of the secondportions P2 of the second device isolation patterns ST2 may have arecessed top surface. In other words, the second portions P2 may beprovided to define recess regions RS4 and RS5. Referring back to FIG.2D, the recess regions RS4 and RS5 may include fourth recess regions RS4between the second active patterns AP2 and fifth recess regions RS5between the first active patterns AP1. Here, the fourth recess regionsRS4 and the fifth recess regions RS5 may have substantially the samerecess depth. This is because the first and second active patterns AP1and AP2 are spaced apart from each other by substantially the samespace, unlike the first region R1. In addition, the second recessregions RS2 on the first region R1 may be provided to have a recessdepth greater than that of the fourth recess regions RS4. In certainembodiments, the first device isolation patterns ST1 may have topsurfaces, which are recessed at a recess depth greater than the fourthand fifth recess regions RS4 and RS5.

On the first and second active patterns AP1 and AP2 of the second regionR2, the gate electrodes GE may be provided to cross the first and secondactive patterns AP1 and AP2 and extend in the first direction D1. Thegate insulating pattern GI may be provided below each of the gateelectrodes GE, and the gate spacers GS may be provided at opposite sidesof each of the gate electrodes GE. In addition, the capping pattern GPmay be provided to cover the top surface of each of the gate electrodesGE.

The first and second source/drain regions SD1 and SD2 may be provided onthe first and second active patterns AP1 and AP2 and at opposite sidesof each of the gate electrodes GE. In the meantime, the secondsource/drain regions SD2 on the first region R1 may be arranged spacedapart from each other in the first direction D1. However, the secondsource/drain regions SD2 on the second region R2 may be merged to eachother to form a single source/drain region extending in the firstdirection D1. This is because a space between the second active patternsAP2 on the second region R2 is smaller than a space between the secondactive patterns AP2 on the first region R1 (i.e., L4<L2).

The etch stop layer 125 may be provided on the second region R2. Theetch stop layer 125 may cover the top surfaces of the first and seconddevice isolation patterns ST1 and ST2 and the first and secondsource/drain regions SD1 and SD2. The etch stop layer 125 may not coverinner surfaces of the fourth recess regions RS4. This may be because thesecond source/drain regions SD2 are merged to each other. By contrast,the etch stop layer 125 may be provided to cover inner surfaces of thefifth recess regions RS5.

The first interlayered insulating layer 130 may be provided on thesecond region R2 to fill gap regions between the gate electrodes GE. Thefirst interlayered insulating layer 130 may fill the fifth recessregions RS5 provided with the etch stop layer 125. By contrast, thefourth recess regions RS4 may not be filled with the first interlayeredinsulating layer 130. In other words, first air gaps AG1 may be formedin the fourth recess regions RS4, respectively, which are positionedbelow the second source/drain regions SD2. The first air gaps AG1 may bea region in which a solid material is not provided and may be asubstantially empty space. For example, the first air gaps AG1 may bedirectly enclosed by the second source/drain regions SD2 and the seconddevice isolation patterns ST2. In other words, the first air gaps AG1may not be enclosed by the etch stop layer 125. Because the first airgaps AG1 are provided below the second source/drain regions SD2,reducing parasitic capacitance between the second active patterns AP2may be possible.

The source/drain contacts CA may be provided at opposite sides of eachof the gate electrodes GE. The source/drain contacts CA may beelectrically connected to the first and second source/drain regions SD1and SD2 through the second interlayered insulating layer 150, the firstinterlayered insulating layer 130, and the etch stop layer 125.

FIGS. 3, 5 and 8 are plan views illustrating a method of fabricating asemiconductor device according to some example embodiments of theinventive concepts. FIGS. 4A to 4C are sectional views taken along linesA-A′, B-B′, C-C′, and D-D′ of FIG. 3, FIGS. 6A to 6D are sectional viewstaken along lines A-A′, B-B′, C-C′, D-D′, and E-E′ of FIG. 5, FIGS. 7Ato 7D are sectional views taken along lines A-A′, B-B′, C-C′, D-D′, andE-E′ of FIG. 5, and FIGS. 9A to 9D are sectional views taken along linesA-A′, B-B′, C-C′, D-D′, and E-E′ of FIG. 8.

Referring to FIGS. 3 and 4A to 4C, a substrate 100 with a first regionR1 and a second region R2 may be provided. In example embodiments, thesubstrate 100 may be a silicon substrate, a germanium substrate, or asilicon-on-insulator (SOI) substrate. The first region R1 may be a partof a memory cell region, on which a plurality of memory cells forstoring data are provided, and the second region R2 may be a part of alogic cell region, on which logic transistors constituting a logiccircuit are provided.

Each of the regions R1 and R2 may include NMOSFET regions NR1 and NR2and PMOSFET regions PR1 and PR2. In some example embodiments, each ofthe NMOSFET regions NR1 and NR2 may be defined as an active region onwhich an n-type transistor is solely integrated, and each of the PMOSFETregion PR1 and PR2 may be defined as an active region on which a p-typetransistor is solely integrated. In each of the regions R1 and R2, theNMOSFET regions NR1 and NR2 and the PMOSFET regions PR1 and PR2 may bearranged in a first direction D1, but the inventive concepts may not belimited thereto.

The regions R1 and R2 of the substrate 100 may be patterned to formfirst trenches 101 defining first active patterns AP1 and secondtrenches 102 defining second active patterns AP2. The first and secondactive patterns AP1 and AP2 may be arranged in the first direction D1and may be line-shaped structures extending in a second direction D2crossing the first direction D1.

The first region R1 of the substrate 100 may be again patterned to formdeep trenches 103. The deep trenches 103 may be formed at opposite sidesof the first NMOSFET region NR1 and the first PMOSFET region PR1. Also,the deep trenches 103 may be formed by patterning the second region R2of the substrate 100. The deep trenches 103 may be formed to have bottomsurfaces that are lower than those of the first and second trenches 101and 102. In the second region R2, the deep trenches 103 may be formedbetween the second NMOSFET and PMOSFET regions NR2 and PR2 to define thesecond NMOSFET and PMOSFET regions NR2 and PR2.

In the first region R1, the first active patterns AP1 may be formed insuch a way that they are spaced apart from each other at a pitch of thefirst length L1, and the second active patterns AP2 may be formed insuch a way that they are spaced apart from each other at a pitch of asecond length L2. An adjacent pair of the first and second activepatterns AP1 and AP2 may be formed in such a way that they are spacedapart from each other by a pitch of a third length L3. Here, the secondlength L2 may be longer than the first length L1, and the third lengthL3 may be longer than the second length L2.

By contrast, in the second region R2, the second active patterns AP2 maybe formed in such a way that they are spaced apart from each other at apitch of a fourth length L4, and the first active patterns AP1 may beformed in such a way that they are spaced apart from each other at apitch of a fifth length L5. Here, the fourth length L4 may besubstantially equal to the fifth length L5.

In each of the regions R1 and R2, first device isolation patterns ST1may be formed in the deep trenches 103, respectively. In addition,second device isolation patterns ST2 may be formed in the first andsecond trenches 101 and 102. The second device isolation patterns ST2may be formed to expose upper portions of the first and second activepatterns AP1 and AP2. The upper portions of the first and second activepatterns AP1 and AP2 exposed by the second device isolation patterns ST2will be referred to as first and second active fins AF1 and AF2,respectively. In some example embodiments, the first and second deviceisolation patterns ST1 and ST2 may be substantially connected to eachother to form a single insulating pattern. The first and second deviceisolation patterns ST1 and ST2 may be formed of or include a siliconoxide layer.

Referring to FIGS. 5 and 6A to 6D, sacrificial gate patterns 110 may beformed on each of the regions R1 and R2 of the substrate 100, and gatemask patterns 115 may be formed on the sacrificial gate patterns 110.The sacrificial gate patterns 110 may be formed to cross the first andsecond active patterns AP1 and AP2 and extend in the first direction D1.Each of the sacrificial gate patterns 110 may be formed to cover top andside surfaces of the first and second active fins AF1 and AF2, andmoreover, the sacrificial gate patterns 110 may extend to cover topsurfaces of the first and second device isolation patterns ST1 and ST2.

The formation of the sacrificial gate patterns 110 and the gate maskpatterns 115 may include sequentially forming a sacrificial gate layerand a gate mask layer on the substrate 100 to cover the first and secondactive fins AF1 and AF2 and patterning the gate mask layer and thesacrificial gate layer. The sacrificial gate layer may be formed of orinclude a poly silicon layer. The gate mask layer may be formed of orinclude a silicon nitride layer or a silicon oxynitride layer.

Because the sacrificial gate patterns 110 are formed to cross the firstand second active fins AF1 and AF2, each of the second device isolationpatterns ST2 may have a first portion P1 and second portions P2. Forexample, the first portion P1 may be a portion of the second deviceisolation pattern ST2 that is positioned below the sacrificial gatepattern 110 and is overlapped with the sacrificial gate pattern 110 in aplan view. The second portions P2 may be other portions of the seconddevice isolation pattern ST2 that are positioned at opposite sides ofthe sacrificial gate pattern 110 and are horizontally separated fromeach other by the first portion P1.

Thereafter, a gate spacer layer 120 may be formed on the substrate 100to conformally cover the sacrificial gate patterns 110. As an example,the gate spacer layer 120 may be formed of or include at least one of asilicon oxide layer, a silicon nitride layer, or a silicon oxynitridelayer. The gate spacer layer 120 may be formed by a deposition process(e.g., a CVD or ALD process). In example embodiments, the gate spacerlayer 120 may be formed to cover the first and second active fins AF1and AF2 exposed by the sacrificial gate patterns 110.

Referring to FIGS. 7A to 7D, the gate spacer layer 120 may beanisotropically etched to form gate spacers GS, and here, the gatespacers GS may be formed to cover opposite side surfaces of each of thesacrificial gate patterns 110. Moreover, the gate spacer layer 120 onthe first and second active fins AF1 and AF2 also may be anisotropicallyetched to form other gate spacers GS, and not drawn here, the other gatespacers GS may be formed to cover opposite side surfaces, which may beexposed by the sacrificial gate patterns 110, of each of the first andsecond active fins AF1 and AF2.

An etching process may be performed to remove upper portions of thefirst and second active patterns AP1 and AP2, which provided on each ofthe regions R1 and R2 and are positioned at opposite sides of each ofthe sacrificial gate patterns 110. The other gate spacers GS on thefirst and second active fins AF1 and AF2 also may be removed during theetching process. The etching process may include forming a mask patternon the substrate 100 and etching the upper portions of the first andsecond active patterns AP1 and AP2 using the mask pattern as an etchmask. The etching process may be performed in a dry and/or wet etchingmanner.

In some example embodiments, the etching process may be performed insuch a way that the second active patterns AP2 are over-etched to havetop surfaces lower than those of the first active patterns AP1.

As a result, each of the first active patterns AP1 may have a first topsurface TSa1, which is etched during the etching process, and a secondtop surface TSa2, which is positioned below the sacrificial gatepatterns 110 and is not etched during the etching process. That is, thesecond top surface TSa2 may be higher than the first top surface TSa1.Each of the second active patterns AP2 may have a first top surfaceTSb1, which is etched during the etching process, and a second topsurface TSb2, which is positioned below the sacrificial gate patterns110 and is not etched during the etching process. That is, the secondtop surface TSb2 may be higher than the first top surface TSb1. In someexample embodiments, the first top surfaces TSa1 and TSb1 of the firstand second active patterns AP1 and AP2 may have a downward roundedprofile.

Because, compared with the first active patterns AP1, the second activepatterns AP2 are more deeply etched, the first top surface TSb1 of eachof the second active patterns AP2 may be lower than the first topsurface TSa1 of each of the first active patterns AP1. Furthermore, awidth W2 of the first top surface TSb1 of the second active pattern AP2may be greater than a width W1 of the first top surface TSa1 of thefirst active pattern AP1. However, the second top surface TSa2 of eachof the first active patterns AP1 may be positioned at substantially thesame level as the second top surface TSb2 of each of the second activepatterns AP2.

When the upper portions of the first and second active patterns AP1 andAP2 are removed from the first region R1, upper portions of the secondportions P2 of the second device isolation pattern ST2 may be recessed.As a result, recess regions RS1, RS2, and RS3 may be formed on thesecond portions P2 of the second device isolation pattern ST2.

For example, first recess regions RS1 may be formed between the firstactive patterns AP1, second recess regions RS2 may be formed between thesecond active patterns AP2 , and third recess regions RS3 may be formedbetween adjacent pairs of the first and second active patterns AP1 andAP2. The first to third recess regions RS1-RS3 may be formed to have arecess depth that is dependent on a pattern density (i.e., a spacebetween the first and second active patterns AP1 and AP2).

Upper portions of the second portions P2 of the second device isolationpattern ST2 on the second region R2 may also be recessed. As a result,recess regions RS4 and RS5 may be formed on the second portions P2,respectively, of the second device isolation pattern ST2.

For example, fourth recess regions RS4 may be formed between the secondactive patterns AP2, and fifth recess regions RS5 may be formed betweenthe first active patterns AP1. The fourth and fifth recess regions RS4and RS5 may be formed to have substantially the same recess depth.

Thereafter, first and second source/drain regions SD1 and SD2 may beformed at opposite sides of each of the sacrificial gate patterns 110.The first source/drain regions SD1 may be formed on the first topsurfaces TSa1 of the first active patterns AP1, respectively, and thesecond source/drain regions SD2 may be formed on the first top surfacesTSb1 of the second active patterns AP2, respectively. In other words,the first source/drain regions SD1 may be formed by a selectiveepitaxial growth process using the first top surfaces TSa1 of the firstactive patterns AP1 as a seed layer. The second source/drain regions SD2may be formed by a selective epitaxial growth process using the firsttop surfaces TSb1 of the second active patterns AP2 as a seed layer.

The first source/drain regions SD1 may be formed to exert a tensilestrain to first channel regions CH1 of the first active fins AF1interposed therebetween. For example, in the case where the substrate100 is a silicon substrate, the first source/drain regions SD1 may beformed of a Si or SiC layer. The first source/drain regions SD1 may bedoped with n-type impurities after or during the epitaxial growthprocess.

By contrast, the second source/drain regions SD2 may be formed to exerta compressive strain to the second channel regions CH2 of the secondactive fins AF2 interposed therebetween. For example, in the case wherethe substrate 100 is a silicon substrate, the second source/drainregions SD2 may be formed of a SiGe layer. The second source/drainregions SD2 may be doped with p-type impurities after or during theepitaxial growth process.

Because the first and second source/drain regions SD1 and SD2 are formedof different materials that are grown through the epitaxial growthprocess, the first and second source/drain regions SD1 and SD2 may bedifferent from each other in terms of their shape or size. For example,the maximum width W3 of the first source/drain regions SD1 may bedifferent from the maximum width W4 in the second direction D2 of thesecond source/drain regions SD2. In addition, the second source/drainregions SD2 may be grown to have high thickness uniformity, comparedwith the first source/drain regions SD1. For example, when viewed in asection taken in the first direction D1, the second source/drain regionsSD2 may have sharp top portions. By contrast, the first source/drainregions SD1 may have flat or truncated top portions.

The second source/drain regions SD2 on the first region R1 may be formedto be spaced apart from each other in the first direction D1. Bycontrast, the second source/drain regions SD2 on the second region R2may be merged to each other during the epitaxial growth process.Accordingly, the second source/drain regions SD2 on the second region R2may constitute a single source/drain region extending in the firstdirection Dl. Because the second source/drain regions SD2 on the secondregion R2 are merged to each other, first air gaps AG1 may be formedbelow the second source/drain regions SD2 on the second region R2. Thefirst air gaps AG1 may be regions that are directly enclosed by thesecond source/drain regions SD2 and the second device isolation patternsST2.

Referring to FIGS. 8 and 9A to 9D, an etch stop layer 125 may beconformally formed on each of the regions R1 and R2. The etch stop layer125 may be formed to cover the first and second device isolationpatterns ST1 and ST2, the first and second source/drain regions SD1 andSD2, and the gate spacers GS. In addition, the etch stop layer 125 maybe formed to cover inner surfaces of the first, second, third, and fifthrecess regions RS1-RS3 and RS5 of the second device isolation patternsST2. The etch stop layer 125 may be formed of a material having an etchselectivity with respect to a first interlayered insulating layer 130 tobe described below. As an example, the etch stop layer 125 may be formedof or include a silicon nitride layer or a silicon oxynitride layer. Theetch stop layer 125 may be formed using a CVD or ALD process.

A first interlayered insulating layer 130 may be formed on the substrate100 provided with the etch stop layer 125. As an example, the firstinterlayered insulating layer 130 may be formed of or include a siliconoxide layer. Thereafter, a planarization process may be performed on thefirst interlayered insulating layer 130 to expose top surfaces of thesacrificial gate patterns 110. The planarization process may include anetch-back process and/or a chemical mechanical polishing (CMP) process.In example embodiments, the planarization process may be performed toremove not only a portion of the etch stop layer 125 but also the gatemask patterns 115, which are provided on the sacrificial gate patterns110.

The sacrificial gate patterns 110 may be removed to form gap regions140, and here, the gap regions 140 may be formed to expose the first andsecond channel regions CH1 and CH2 of the first and second active finsAF1 and AF2 between the gate spacers GS. In some example embodiments,the gap regions 140 may be formed by an etching process of selectivelyremoving the sacrificial gate patterns 110.

An oxidation process using plasma may be performed on the first andsecond channel regions CH1 and CH2, and as a result, interface layers ILmay be grown from the first and second channel regions CH1 and CH2,respectively. In other words, the interface layer IL may be formed bythermally or chemically oxidizing the exposed surfaces of the first andsecond channel regions CH1 and CH2. Plasma generated from at least oneof oxygen (O₂), ozone (O₃), or steam (H₂O) may be used in the oxidationprocess. The interface layers IL may be formed of or include a siliconoxide layer.

A gate insulating pattern GI and a gate electrode GE may be sequentiallyformed to fill each of the gap regions 140. In detail, a gate insulatinglayer may be formed to partially fill the gap regions 140. The gatedielectric layer may be formed to cover the top surfaces of the firstand second active fins AF1 and AF2. As an example, the gate dielectriclayer may be formed of at least one of a silicon oxide layer, a siliconoxynitride layer, or high-k dielectric layers, whose dielectricconstants are higher than that of the silicon oxide layer. A gateconductive layer may be formed on the gate dielectric layer to fill theremaining portions of the gap regions 140. As an example, the gateconductive layer may be formed of or include at least one of dopedsemiconductor, conductive metal nitrides, or metals. The gate dielectriclayer and the gate conductive layer may be planarized, and as a result,the gate insulating pattern GI and the gate electrode GE may be formedin each of the gap regions 140.

The gate insulating patterns GI and gate electrodes GE in the gapregions 140 may be partially recessed, and capping patterns GP may beformed on the gate electrodes GE, respectively. As an example, thecapping patterns GP may be formed of or include at least one of asilicon oxide layer, a silicon nitride layer, or a silicon oxynitridelayer.

Referring back to FIGS. 1 and 2A to 2D, a second interlayered insulatinglayer 150 may be formed on the first interlayered insulating layer 130.As an example, the second interlayered insulating layer 150 may beformed using a silicon oxide layer.

Source/drain contacts CA may be formed at opposite sides of each of thegate electrodes GE. For example, contact holes may be formed topenetrate the second interlayered insulating layer 150, the firstinterlayered insulating layer 130, and the etch stop layer 125 and toexpose the first and second source/drain regions SD1 and SD2. In exampleembodiments, upper portions of the first and second source/drain regionsSD1 and SD2 may be partially etched, when the contact holes are formed.Thereafter, a first conductive pattern 160 and a second conductivepattern 165 may be sequentially formed to fill each of the contactholes. The first conductive pattern 160 may be a barrier conductivelayer and may be formed of or include at least one of a titanium nitridelayer, a tungsten nitride layer, or a tantalum nitride layer. The secondconductive pattern 165 may be a metal layer and may be formed of orinclude at least one of tungsten, titanium, or tantalum.

Although not shown, interconnection lines may be formed on the secondinterlayered insulating layer 150 and may be coupled to the source/draincontacts CA, respectively. The interconnection lines may be formed of orinclude at least one of conductive materials.

FIG. 10 is a sectional view that is taken along line D-D′ of FIG. 1 toillustrate a semiconductor device according to some example embodimentsof the inventive concepts. In the following description, an elementpreviously described with reference to FIGS. 1 and 2A to 2D may beidentified by a similar or identical reference number without repeatingan overlapping description thereof, for the sake of brevity.

Referring to FIGS. 1 and 10, the first source/drain regions SD1 on thefirst region R1 may be merged to form a single source/drain regionextending in the first direction D1. Unlike that shown in FIG. 2C, thefirst source/drain regions SD1 may be merged to each other, but they maybe grown in a relatively irregular manner.

The first air gaps AG1 may be formed below the first source/drainregions SD1 and in the first recess regions RS1, respectively. The firstair gaps AG1 may be directly enclosed by the first source/drain regionsSD1 and the second device isolation patterns ST2. In other words, thefirst air gaps AG1 may not be enclosed by the etch stop layer 125.Because the first air gaps AG1 are provided below the first source/drainregions SD1, reducing parasitic capacitance between the first activepatterns AP1 may be possible.

On the first region R1, the etch stop layer 125 may be formed to fillgap regions between the second source/drain regions SD2 adjacent to eachother. For example, the etch stop layer 125 may be conformally formed onthe second source/drain regions SD2 in such a way that the gap regionsbetween the second source/drain regions SD2 are sealed by the etch stoplayer 125. Accordingly, second air gaps AG2 may be formed in the secondrecess regions RS2, respectively.

Unlike the first air gaps AG1, the second air gaps AG2 may be coveredwith the etch stop layer 125. Because the second recess regions RS2 areformed to have bottom surfaces lower than those of the first recessregions RS1, the second air gaps AG2 may be larger than the first airgaps AG1. Because the second air gaps AG2 are provided below the secondsource/drain regions SD2, reducing parasitic capacitance between thesecond active patterns AP2 may be possible.

FIG. 11 is a sectional view that is taken along line D-D′ of FIG. 1 toillustrate a semiconductor device according to some example embodimentsof the inventive concepts. In the following description, an elementpreviously described with reference to FIGS. 1 and 2A to 2D may beidentified by a similar or identical reference number without repeatingan overlapping description thereof, for the sake of brevity.

Referring to FIGS. 1 and 11, the first source/drain regions SD1 on thefirst region R1 may be merged to form a single source/drain regionextending in the first direction D1. The first air gaps AG1 may beformed below the first source/drain regions SD1 and in the first recessregions RS1, respectively.

First residue patterns 123 may be provided adjacent to interfacesbetween the second source/drain regions SD2 and the second activepatterns AP2. The first residue patterns 123 may be formed between anadjacent pair of the second active patterns AP2. By contrast, the firstresidue patterns 123 may not be formed between an adjacent pair of thefirst active pattern AP1 and the second active pattern AP2.

As previously described with reference to FIGS. 6C and 7C, the gatespacer layer 120 covering the first and second active patterns AP1 andAP2 may be removed when the upper portions of the first and secondactive patterns AP1 and AP2 are recessed. However, in exampleembodiments, a portion of the gate spacer layer 120 may not be removedfrom the gap regions between the second active patterns AP2, therebyforming the first residue pattern 123. Owing to the presence of thefirst residue patterns 123, upper portions of the second active patternsAP2 may be incompletely recessed, and thus, the first top surfaces TSb1of the second active patterns AP2 may be an inclined or asymmetricprofile, unlike the first top surfaces TSa1 of the first active patternsAP1.

Owing to the presence of the first residue patterns 123 and/or theinclined or asymmetric profile of the first top surfaces TSb1, thesecond source/drain regions SD2 may be at an angle to the top surface ofthe substrate 100. For example, the second source/drain region SD2 maybend toward the first source/drain region SD1 adjacent thereto.

FIG. 12 is a sectional view that is taken along line D-D′ of FIG. 1 toillustrate a semiconductor device according to some example embodimentsof the inventive concepts. In the following description, an elementpreviously described with reference to FIGS. 1 and 2A to 2D may beidentified by a similar or identical reference number without repeatingan overlapping description thereof, for the sake of brevity.

Referring to FIGS. 1 and 12, second residue patterns 124 may be formedto be adjacent to interfaces between the first source/drain regions SD1and the first active patterns AP1 and on the first region R1. Forexample, the second residue patterns 124 may be formed on opposite sidesurfaces of a lower portion of at least one of the first source/drainregions SD1. When measured in the first direction D1, the at least oneof the first source/drain regions SD1 may have an increasing width fromthe second residue patterns 124.

As previously described with reference to FIGS. 6C and 7C, the gatespacer layer 120 covering the first and second active patterns AP1 andAP2 may be removed when the upper portions of the first and secondactive patterns AP1 and AP2 are recessed. However, in exampleembodiments, a portion of the gate spacer layer 120 may not be removedfrom opposite sides of each of the first active patterns AP1, therebyforming the second residue patterns 124.

According to some example embodiments of the inventive concepts, asemiconductor device may be configured to include NMOS and PMOS-FETshaving source/drain structures different from each other. Thisconfiguration may allow improvement to electric characteristics of NMOSand PMOSFETs independently.

While example embodiments of the inventive concepts have beenparticularly shown and described, it will be understood by one ofordinary skill in the art that variations in form and detail may be madetherein without departing from the spirit and scope of the attachedclaims.

What is claimed is:
 1. A semiconductor device, comprising: a substrateincluding an NMOSFET region and a PMOSFET region; a plurality of firstactive fins on the NMOSFET region; a plurality of second active fins onthe PMOSFET region; a gate electrode on the first and second activefins, the gate electrode extending in a first direction; a firstsource/drain pattern on the first active fins; and a second source/drainpattern on the second active fins, wherein the first and secondsource/drain patterns are adjacent to a side of the gate electrode,wherein a lowermost bottom surface of the first source/drain pattern ispositioned at a first level, wherein a lowermost bottom surface of thesecond source/drain pattern is positioned at a second level, and whereinthe first level is higher than the second level.
 2. The semiconductordevice of claim 1, wherein a pitch between the first active fins issubstantially the same with a pitch between the second active fins. 3.The semiconductor device of claim 1, wherein one of the first activefins has a first top surface contacting the lowermost bottom surface ofthe first source/drain pattern, wherein one of the second active finshas a second top surface contacting the lowermost bottom surface of thesecond source/drain pattern, wherein the first top surface has a firstwidth in the first direction, and wherein the second top surface has asecond width greater than the first width in the first direction.
 4. Thesemiconductor device of claim 1, further comprising: a first deviceisolation layer between the NMOSFET region and the PMOSFET region; asecond device isolation layer between a pair of the first active fins;and a third device isolation layer between a pair of the second activefins, wherein a thickness of the first device isolation layer is greaterthan a thickness of the second device isolation layer, and wherein thethickness of the first device isolation layer is greater than athickness of the third device isolation layer.
 5. The semiconductordevice of claim 4, wherein the thickness of the second device isolationlayer is substantially the same with the thickness of the third deviceisolation layer.
 6. The semiconductor device of claim 4, wherein a widthof the first device isolation layer is greater than a width of thesecond device isolation layer, and wherein the width of the first deviceisolation layer is greater than a width of the third device isolationlayer.
 7. The semiconductor device of claim 1, further comprising an airgap under the second source/drain pattern and between a pair of thesecond active fins.
 8. The semiconductor device of claim 1, furthercomprising an etch stop layer covering an outer surface of the firstsource/drain pattern and an outer surface of the second source/drainpattern.
 9. The semiconductor device of claim 1, wherein the firstsource/drain pattern is a first epitaxial pattern formed by a firstselective epitaxial growth process using top surfaces of the firstactive fins as a first seed layer, and wherein the second source/drainpattern is a second epitaxial pattern formed by a second selectiveepitaxial growth process using top surfaces of the second active fins asa second seed layer.
 10. The semiconductor device of claim 1, whereinthe first source/drain pattern has a different shape from the secondsource/drain pattern.
 11. A semiconductor device, comprising: asubstrate including a first region and a second region; a first activefin on the first region of the substrate; a second active fin on thefirst region of the substrate; a third active fin on the second regionof the substrate, the second active fin being between the first activefin and the third active fin; a fourth active fin on the second regionof the substrate, the third active fin being between the second activefin and the fourth active fin; a gate electrode on the first, second,third and fourth active fins; a first source/drain pattern on each ofthe first and second active fins; and a second source/drain pattern oneach of the third and fourth active fins, wherein the first source/drainpattern has a different conductivity from that of the secondsource/drain pattern, and wherein a lowermost bottom of a first recessbetween the first and second active fins is higher than a lowermostbottom of a second recess between the third and fourth active fins. 12.The semiconductor device of claim 11, wherein a lowermost bottom of athird recess between the second and third active fins is lower than thelowermost bottom of the second recess.
 13. The semiconductor device ofclaim 11, wherein the first source/drain pattern has a bottom surfacecontacting a top surface of each of the first and second active fins,wherein the second source/drain pattern has a bottom surface contactinga top surface of each of the third and fourth active fins, and whereinthe bottom surface of the first source/drain pattern is higher than thebottom surface of the second source/drain pattern.
 14. The semiconductordevice of claim 11, wherein a distance between a top portion of thefirst active fin and a top portion of the second active fin is differentfrom a distance between the top portion of the second active fin and atop portion of the third active fin.
 15. The semiconductor device ofclaim 11, wherein the first region is an NMOSFET region, and the secondregion is a PMOSFET region.
 16. A semiconductor device, comprising:first and second active patterns protruding upward from a substrate; agate electrode crossing the first and second active patterns, the gateelectrode extending in a first direction; a first source/drain region onthe first active pattern and on at least one side of the gate electrode,the first source/drain region having a first bottom surface in contactwith a first top surface of the first active pattern; and a secondsource/drain region on the second active pattern and on at least oneside of the gate electrode, the second source/drain region having aconductivity type different from that of the first source/drain region,the second source/drain region having a second bottom surface in contactwith a second top surface of the second active pattern and at a lowerlevel than the first bottom surface, wherein the first top surface ofthe first active pattern has a first width in the first direction,wherein the second top surface of the second active pattern has a secondwidth greater than the first width in the first direction, and wherein alowermost bottom of a first recess between the first source/drain regionand the second source/drain region is lower than a lowermost bottom of asecond recess adjacent to the first source/drain region.
 17. Thesemiconductor device of claim 16, wherein the lowermost bottom of thefirst recess is lower than a lowermost bottom of a third recess adjacentto the second source/drain region.
 18. The semiconductor device of claim17, wherein the lowermost bottom of the second recess is higher than thelowermost bottom of the third recess.
 19. The semiconductor device ofclaim 16, wherein the first active pattern and the first source/drainregion constitute an NMOSFET; and wherein the second active pattern andthe second source/drain region constitute a PMOSFET.
 20. Thesemiconductor device of claim 16, wherein the first bottom surface ofthe first source/drain region is higher than the second bottom surfaceof the second source/drain region.